The invention relates to active adaptive control systems, and more particularly to an improvement for intentionally selectively constraining performance when control is undesired.
The invention arose during continuing development efforts directed toward active acoustic attenuation systems. Active acoustic attenuation involves injecting a canceling acoustic wave to destructively interfere with and cancel an input acoustic wave. In an active acoustic attenuation system, the output acoustic wave is sensed with an error transducer, such as a microphone or an accelerometer, which supplies an error signal to an adaptive filter control model which in turn supplies a correction signal to a canceling output transducer, such as a loudspeaker or a shaker, which injects an acoustic wave to destructively interfere with the input acoustic wave and cancel same such that the output acoustic wave at the error transducer is zero or some other desired value.
An active adaptive control system minimizes an error signal by introducing a control signal from an output transducer to combine with the system input signal and yield a system output signal. The system output signal is sensed with an error transducer providing the error signal. An adaptive filter model has an error input from the error signal, and outputs a correction signal to the output transducer to introduce a control signal matching the system input signal, to minimize the error signal.
The present invention is applicable to active adaptive control systems, including active acoustic attenuation systems. In the present invention, the adaptive filter model is provided with a pair of error inputs. The system drives the first error input to drive the correction signal toward a value matching the system input signal, and selectively drives the second error input to drive the correction signal away from the matching signal by instead driving the correction signal towards zero. A spectral leak signal is selectively supplied to the second error input in response to a given condition of a given parameter, such that in the presence of the given condition, the spectral leak signal drives the correction towards zero, and such that in the absence of the given condition, the error signal from the error transducer drives the correction signal towards the noted matching value.
The method of the present invention involves selectively constraining performance of the model by driving the output of the model towards zero in response to a given condition of a given parameter. In preferred form, the output of the model is driven towards zero by driving the output of the model towards the error input, such that when the model adapts to drive the error signal towards zero, the output of the model is also driven towards zero. This is preferably accomplished by providing a copy of the model and supplying the output of the copy to the error input, such that the model adapts to drive the error input towards zero which in turn requires that the output of the copy and hence the output of the model are driven towards zero to provide the noted constrained performance when modification and/or cancellation of the system input signal by the model is undesired.